Seb's keyblade, Burning Light

The difference: Only Seb can use this weapon, he can call upon it whenever he chooses. The chain makes him more resilient to fire, but he has to evoke (use) this ability.

Weakness: This keyblade cannot leave Seb's hand when called upon. If it does, he has to recall it. Which is not very convenient. Also, when evoking the power of it's chain, Seb gets damaged more by ice, and less by fire.